Questions and Answers
What is a key principle of network design?
What is a characteristic of a bad network design?
What is the primary function of the distribution layer in a two-tier architecture?
What is an example of a distribution layer switch?
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What is the primary benefit of adding redundant connections and devices in a network design?
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What is the primary function of the core layer in a three-tier architecture?
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What is a characteristic of a three-tier architecture?
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What is a benefit of using a two-tier architecture?
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What is the primary function of core layer switches in a three-tier architecture?
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Which of the following statements is true about the core layer in a three-tier network design model?
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What is the main difference between the three-tier and two-tier network design models?
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Which Cisco core switch series is a high-end, modular core switch with a 25.6 terabit per second backplane?
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What is the main advantage of the three-tier network design model?
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What is the primary benefit of a well-designed network?
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What is the role of the distribution layer in a two-tier network design model?
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What is the primary characteristic of core switches?
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Study Notes
Network Design Principles
- A network design should not have single points of failure, which are devices or connections that can cause the entire network to fail if they fail.
- A single point of failure can be a router, switch, or cable that connects devices.
Bad Network Design
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A bad network design can be similar to a home network, where one device (e.g., router) performs multiple functions (e.g., routing, switching, modulating).
Having a single device perform multiple functions can lead to several problems, particularly in larger or more complex networks. Here are some reasons why this is often considered a bad design:
1. Single Point of Failure: When one device manages multiple critical functions, its failure can bring the entire network down. Distributing these roles across multiple devices increases redundancy and reliability.
2. Performance Bottlenecks: Different functions often require different resources. A single device may struggle to efficiently manage all tasks simultaneously, leading to bottlenecks and reduced performance.
3. Limited Scalability: As the network grows, a single multi-function device may not be able to handle the increased load. Dedicated devices for specific tasks can be scaled independently to meet the needs of a growing network.
4. Security Risks: Multi-functional devices can introduce security vulnerabilities. If one function is compromised, it could potentially expose other functions. Segregating duties across different devices can better isolate and protect each function.
5. Complex Troubleshooting: Diagnosing problems can be more complex if a single device handles multiple roles. Isolating the issue might require deeper investigation compared to a scenario where distinct devices with clear functions are involved.
6. Specialization: Devices designed for specific tasks often perform more efficiently and with better features than a multi-purpose device. For example, a dedicated firewall will typically offer better security features than a multi-functional router.
7. Firmware and Software Limitations: Multi-function devices might not receive updates and improvements for all functionalities as promptly as specialized devices, leading to outdated features and potential compatibility issues.
Overall, separating the roles of routing, switching, and other network functions across different devices can enhance performance, reliability, security, and scalability.
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In a bad network design, adding devices can lead to a daisy chain of switches, which can cause single points of failure.
Two-Tier Architecture
A two-tier architecture is a network design that consists of two layers: access layer and distribution layer.
The access layer is where devices (e.g., computers, servers) connect to switches.
The distribution layer is where switches connect to a router and distribute traffic throughout the network.
The distribution layer is also responsible for route filtering, VLAN routing, management, ACLs, IPS security policies, routing, and summarization.
Advantages of Two-Tier Architecture:
1. Simplicity: The design is straightforward and easy to manage due to its simple structure with only two layers.
2. Cost-Effective: Reduces the cost of infrastructure as it requires fewer devices and cables compared to more complex architectures.
3. Improved Performance: Minimizes network latency and congestion as there are fewer hops between devices and the core network.
4. Ease of Troubleshooting: Simplified network layout makes it easier to diagnose and resolve issues.
5. Scalability: Easier to expand by adding more switches at the access layer without significantly affecting the existing structure.
Disadvantages of Two-Tier Architecture:
1. Limited Scalability: May not be suitable for very large networks as it can become cumbersome to manage and expand beyond a certain point.
2. Data Bottlenecks: Potential for bottlenecks at the distribution layer as all traffic must pass through this layer.
3. Redundancy Issues: Limited redundancy options compared to more complex architectures, which can impact network reliability.
4. Performance Constraints: May not adequately support high-density environments or complex applications that require advanced networking features.
5. Security Concerns: With fewer layers, there are fewer checkpoints to apply security measures, making the network potentially more vulnerable to attacks.
Distribution Layer Switches
- Distribution layer switches are high-performance switches that can handle a lot of traffic.
- Examples of distribution layer switches include Cisco Catalyst 3850 and Cisco Catalyst 6500.
Redundancy in Network Design
- Adding redundant connections and devices can help eliminate single points of failure.
- Redundancy can be achieved by adding multiple distribution layer switches, routers, and connections between them.
Three-Tier Architecture
- A three-tier architecture is a network design that consists of three layers: access layer, distribution layer, and core layer.
- The core layer is where high-performance switches (e.g., core switches) connect multiple distribution layer switches.
- The core layer is used in large networks where multiple buildings or locations need to be connected.
Core Layer Switches
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Core layer switches are high-performance switches that can handle a lot of traffic and are used in the core layer of a three-tier architecture.
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Core layer switches are responsible for connecting multiple distribution layer switches and routing traffic between them.### Cisco Three-Tier Network Design Model
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The three-tier model consists of the access layer, distribution layer, and core layer.
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The access layer connects devices such as phones and computers.
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The distribution layer connects to the access layer and the core layer.
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The core layer is the backbone of the network, handling high traffic and providing low latency and high reliability.
Core Layer
- The core layer is associated with high-speed, low-latency, and high-reliability connections.
- It is responsible for handling a large amount of traffic.
- Core switches are expensive, reliable, and powerful.
Two-Tier Network Design Model (Collapsed Core)
- In the two-tier model, the core layer is collapsed into the distribution layer.
- The distribution layer takes on the responsibilities of the core layer, making it a powerful and crucial component.
- This model is often used in smaller networks and is simpler in design.
Comparison of Three-Tier and Two-Tier Models
- The three-tier model is more scalable and suitable for larger campuses with multiple buildings because it enables a more flexible and distributed architecture. This allows for easier maintenance and upgrade of individual components without affecting the entire network. Additionally, it provides better separation of concerns, enabling each tier to be managed independently, which is particularly important in environments where there are multiple interconnected buildings.
- On the other hand, the two-tier model is simpler and more suitable for smaller networks due to its reduced complexity and increased manageability. With a two-tier architecture, all network operations and management are concentrated in a single location, making it easier to troubleshoot and maintain. This simplicity also makes the two-tier model more suitable for small to medium-sized organizations with limited IT resources.
Cisco Core Switches
- Cisco offers a range of core switches, from smaller to larger models.
- The Cisco Catalyst 9600 series is a high-end, modular core switch with a 25.6 terabit per second backplane.
- It is designed to be highly reliable and future-proof.
Network Design and Scaling
- A well-designed network can scale easily and handle high traffic.
- A three-tier model can simplify network design and improve scalability.
- Cisco provides documentation and examples of network design and implementation.
Network Design Principles
- Network design should avoid single points of failure, which can cause the entire network to fail if they fail.
- Single points of failure can be devices or connections, such as routers, switches, or cables.
Bad Network Design
- A bad network design can be similar to a home network, where one device performs multiple functions.
- Adding devices to a bad network design can lead to a daisy chain of switches, causing single points of failure.
Two-Tier Architecture
- A two-tier architecture consists of two layers: access layer and distribution layer.
- The access layer is where devices connect to switches.
- The distribution layer connects switches to a router and distributes traffic throughout the network.
- The distribution layer is responsible for route filtering, VLAN routing, management, ACLs, IPS security policies, routing, and summarization.
Distribution Layer Switches
- Distribution layer switches are high-performance switches that can handle a lot of traffic.
- Examples of distribution layer switches include Cisco Catalyst 3850 and Cisco Catalyst 6500.
Redundancy in Network Design
- Adding redundant connections and devices can help eliminate single points of failure.
- Redundancy can be achieved by adding multiple distribution layer switches, routers, and connections between them.
Three-Tier Architecture
- A three-tier architecture consists of three layers: access layer, distribution layer, and core layer.
- The core layer connects multiple distribution layer switches using high-performance switches.
- The core layer is used in large networks where multiple buildings or locations need to be connected.
Core Layer Switches
- Core layer switches are high-performance switches that can handle a lot of traffic and are used in the core layer of a three-tier architecture.
- Core layer switches are responsible for connecting multiple distribution layer switches and routing traffic between them.
Cisco Three-Tier Network Design Model
- The three-tier model consists of the access layer, distribution layer, and core layer.
- The access layer connects devices such as phones and computers.
- The distribution layer connects to the access layer and the core layer.
- The core layer is the backbone of the network, handling high traffic and providing low latency and high reliability.
Core Layer
- The core layer is associated with high-speed, low-latency, and high-reliability connections.
- It is responsible for handling a large amount of traffic.
- Core switches are expensive, reliable, and powerful.
Two-Tier Network Design Model (Collapsed Core)
- In the two-tier model, the core layer is collapsed into the distribution layer.
- The distribution layer takes on the responsibilities of the core layer, making it a powerful and crucial component.
- This model is often used in smaller networks and is simpler in design.
Comparison of Three-Tier and Two-Tier Models
- The three-tier model is more scalable and suitable for larger campuses with multiple buildings.
- The two-tier model is simpler and more suitable for smaller networks.
Cisco Core Switches
- Cisco offers a range of core switches, from smaller to larger models.
- The Cisco Catalyst 9600 series is a high-end, modular core switch with a 25.6 terabit per second backplane.
- It is designed to be highly reliable and future-proof.
Network Design and Scaling
- A well-designed network can scale easily and handle high traffic.
- A three-tier model can simplify network design and improve scalability.
- Cisco provides documentation and examples of network design and implementation.
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Description
Learn about the principles of good network design, including avoiding single points of failure, and common mistakes to avoid in network design, such as overly reliant devices.
